How to Read a Lumber Grade Stamp
"Those of us who have been around lumber for a long time know we can find information about the grade, species, and dryness of a piece of lumber on a ... marking stamped on each piece of wood. Very few know what the rest of the stamp means or what the subtle differences between similar stamps indicate."
Those of us who've been around lumber for a long time know we can find information about the grade, species, and dryness of a piece of lumber on an obscure and at times difficult-to-read ink marking stamped on each piece of wood. Very few know what the rest of the stamp means or what the subtle differences between similar stamps indicate.
Grade Stamps 101
Let's take a look at a lumber stamp in general and then look specifically at some of the stamps you'd find at Dunn Lumber.
In this example, the stamp gives the following information:
- Species Group: SPF (Engelmann Spruce, Lodgepole Pine, and Balsam Fir)
- Moisture Content: Kiln dried to 19% or less and heat treated for export (130° F for 30 minutes to kill bug larva)
- Grade: Number 2 (in this case it's a minimum grade, as in "#2 or better")
- Grade certified by: Canadian Lumber Standards Agency
- Produced at: NLGA mill designation 124
The "Hampton Premium" stamp appears on the same piece of lumber as the mill stamp above (the one that reads "NLGA No 2," among other things). Much of the lumber you'll find at Dunn have additional stamps that refer to appearance qualities not associated with the grade stamp. (Grades relate primarily to strength.) Although you'll find fewer strength-affecting defects in higher grades of lumber—for example #1 will appear better than #3—there are many potential defects that have little affect on strength. Wane, color, and small tight knots may be allowed in the grade but not allowed in the appearance specifications called out in the additional stamp. This transparency is one of the main reasons you'll find our lumber is superior to the box stores.
Here's a 2x4 manufactured here in Washington.
- Grade: Stud (this allows for a few more defects than #2 because the compression strength of lumber endwise is so much stronger than the flex strength for a horizontal member)
- Moisture Content: Kiln dried to 19% or less and heat treated for export (130° F for 30 minutes to kill bug larva)
- Species Group: Hem/Fir (allows Western Hemlock and true firs—Noble, White, and Grand to name a few)
- Grade certified by: US Western Wood Products Association
- Produced at: WWP mill designation 115 (Interfor, Port Angeles, WA)
If the producer gets logs from US and Canadian sources, both stamps are required. HF-N is stronger.
This stud is similar to the one above except it originated from a different mill and is a Douglas Fir, which is not a true fir. Douglas Fir is denser and stronger than Hemlock, and true firs are sometimes grouped with Western Larch.
Learn more
So, that's a quick look at grade stamps! One thing to remember is that different species will naturally reflect different strengths, for the same dimension and grade. You'll find helpful information here and here about the basic idea of "relative strength."
If you have any questions about lumber markings, write them in the comments below. And as always, if there's anything I can answer beyond this or anything I can do to help make you successful, please email me at mikedunn@dunnlumber.com.
